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Java TreeMap pollLastEntry() Method
Description
The Java TreeMap pollLastEntry() method is used to remove and returns a key-value mapping associated with the greatest key in this map, or null if the map is empty.
Declaration
Following is the declaration for java.util.TreeMap.pollLastEntry() method.
public Map.Entry<K,V> pollLastEntry()
Parameters
NA
Return Value
The method call returns the removed last entry of this map, or null if this map is empty.
Exception
NA
Getting Last Entry from a TreeMap of Integer,Integer Pair Example
The following example shows the usage of Java TreeMap pollLastEntry() method to remove and get a key-value mapping associated with the greatest key in this map. We've created a TreeMap object of Integer,Integer pairs. Then few entries are added, map is printed then using pollLastEntry() we're printing a returned value for a given key and map is printed again to see the effect of removing an entry.
package com.tutorialspoint; import java.util.TreeMap; public class TreeMapDemo { public static void main(String[] args) { // creating tree map TreeMap<Integer, Integer> treemap = new TreeMap<>(); // populating tree map treemap.put(2, 2); treemap.put(1, 1); treemap.put(3, 3); treemap.put(6, 6); treemap.put(5, 5); // polling last entry System.out.println("Value before poll: "+ treemap); System.out.println("Value returned: "+ treemap.pollLastEntry()); System.out.println("Value after poll: "+ treemap); } }
Output
Let us compile and run the above program, this will produce the following result.
Value before poll: {1=1, 2=2, 3=3, 5=5, 6=6} Value returned: 6=6 Value after poll: {1=1, 2=2, 3=3, 5=5}
Getting Last Entry from a TreeMap of Integer,String Pair Example
The following example shows the usage of Java TreeMap pollLastEntry() method to remove and get a key-value mapping associated with the greatest key in this map. We've created a TreeMap object of Integer,String pairs. Then few entries are added, map is printed then using pollLastEntry() we're printing a returned value for a given key and map is printed again to see the effect of removing an entry.
package com.tutorialspoint; import java.util.TreeMap; public class TreeMapDemo { public static void main(String[] args) { // creating tree map TreeMap<Integer, String> treemap = new TreeMap<>(); // populating tree map treemap.put(2, "two"); treemap.put(1, "one"); treemap.put(3, "three"); treemap.put(6, "six"); treemap.put(5, "five"); // polling last entry System.out.println("Value before poll: "+ treemap); System.out.println("Value returned: "+ treemap.pollLastEntry()); System.out.println("Value after poll: "+ treemap); } }
Output
Let us compile and run the above program, this will produce the following result.
Value before poll: {1=one, 2=two, 3=three, 5=five, 6=six} Value returned: 6=six Value after poll: {1=one, 2=two, 3=three, 5=five}
Getting Last Entry from a TreeMap of Integer,Object Pair Example
The following example shows the usage of Java TreeMap pollLastEntry() method to remove and get a key-value mapping associated with the greatest key in this map. We've created a TreeMap object of Integer,Student pairs. Then few entries are added, map is printed then using pollLastEntry() we're printing a returned value for a given key and map is printed again to see the effect of removing an entry.
package com.tutorialspoint; import java.util.TreeMap; public class TreeMapDemo { public static void main(String[] args) { // creating tree map TreeMap<Integer, Student> treemap = new TreeMap<>(); // populating tree map treemap.put(2, new Student(2, "Robert")); treemap.put(1, new Student(1, "Julie")); treemap.put(3, new Student(3, "Adam")); treemap.put(6, new Student(6, "Julia")); treemap.put(5, new Student(5, "Tom")); // polling last entry System.out.println("Value before poll: "+ treemap); System.out.println("Value returned: "+ treemap.pollLastEntry()); System.out.println("Value after poll: "+ treemap); } } class Student { int rollNo; String name; Student(int rollNo, String name){ this.rollNo = rollNo; this.name = name; } @Override public String toString() { return "[ " + this.rollNo + ", " + this.name + " ]"; } @Override public boolean equals(Object obj) { if(obj == null) return false; Student s = (Student)obj; return this.rollNo == s.rollNo && this.name.equalsIgnoreCase(s.name); } }
Output
Let us compile and run the above program, this will produce the following result.
Value before poll: {1=[ 1, Julie ], 2=[ 2, Robert ], 3=[ 3, Adam ], 5=[ 5, Tom ], 6=[ 6, Julia ]} Value returned: 6=[ 6, Julia ] Value after poll: {1=[ 1, Julie ], 2=[ 2, Robert ], 3=[ 3, Adam ], 5=[ 5, Tom ]}
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